Private Information Retrieval Schemes and their Applications

• Main Authors: Chun-Hua Chen, 陳俊華
• Other Authors: Gwoboa Horng
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/08573431891642343437

博士 === 國立中興大學 === 資訊科學與工程學系 === 96 === In the internet environment, the protection of users’ privacy from a server had not been considered feasible until the private information retrieval (PIR) problem was stated and solved. A PIR scheme allows a user to retrieve data items from an online database while hiding the identity of the items from a database server. The research of PIR was initiated by Chor et al. in 1995. The communication complexity of retrieving one out of n bits is a method to measure the cost of PIR schemes. It has been proved that the communication complexity of one-server scheme is O(n) in information theoretic security condition. The “n” is the size of database. However, it is unacceptable in real application. But through using a k-server scheme, the communication complexity of a PIR scheme had been improved to O(n1/k) by Chor et al. Some subsequent research of PIR was focused on reducing the communication complexity on k-server PIR schemes. In this dissertation, we point out the serious shortcoming of k-server PIR schemes because of big overhead of management of these severs. It’s astonishing that Kushilevitz et al. proposed a one-server PIR scheme based on the quadratic residue assumption in computational security condition, which is lower than information-theoretic security. Kushilevitz’s PIR scheme conquers the problem of heavy overheads in managing severs of k-server schemes. But, we find out the drawback of Kushilevitz’s PIR scheme. Kushilevitz’s PIR scheme reveals server’s privacy to the user. In the real applications, the user pays a fee in every query. So, it’s not fair to the server side. In this dissertation, we present a one-server PIR scheme with fair privacy on the user side and the server side to conquer the drawback. In Chapter 3 and Chapter 4 of this dissertation, we focus on the application of PIR schemes. In Chapter 3, we consider of protecting customer’s privacy in querying valuable information on the internet. We present the solution which is a PIR scheme with e-payment function. In Chapter 4, we use the concept of a one-server PIR scheme in e-voting. A novel practical e-voting system with low cost and good efficiency is proposed. The PIR schemes proposed in Chapter 3 and Chapter 4 use SC (secure coprocessor) in the scheme to promote the efficiency. The concept is inspired by Smith and Asonov. In Chapter 5 of this dissertation, we point out the security leak of their PIR schemes with SC, proposing our PIR scheme with SC to strengthen the security. In summary, this dissertation introduces PIR schemes and presents a computational one-server PIR scheme to achieve the fair privacy between the server side and the user side. We also make effort on the applications of PIR schemes to build e-payment function and to set up a one-server e-voting system. Finally, in this dissertation we strengthen the security of PIR schemes with SC.